Download Chapter 2: Understanding the Human Body

C17/1:Wellness Guidelines: Healthful Life
Understanding the Human Body
Chapter 2: Understanding the Human Body
Introduction
2.1 Introduction
One of the first steps to achieve good health knows the importance
of caring for your body systems. Are you familiar with those
systems? Do you know when your body is not functioning as it should?
Your body has many systems that work together. Broadly speaking,
you can divide body systems as the following:
1-Support and Control Systems include:
- The skeletal and muscular systems.
- The integumentary system [skin].
- The nervous system.
2-Energy and Transport Systems include:
- The digestive system.
- The circulatory system.
- The respiratory system.
- The urinary system.
3-Endocrine and Reproductive Systems:
- The endocrine system.
- The male and female reproductive systems.
Support and
Control
System
2.2 Support and Control Systems
Objectives: you will be able to describe the functions of the skeletal
and muscular systems and their relationship to health.
Think about a car. It is made of many different parts. The framework
gives the car a definite style and also protects the engine and other
inner structures. The car has an ignition system for starting the
engine. Other systems work together to keep the engine running
smoothly. Some mechanical parts in the car are capable of motion.
These parts will move only if other factors are present and functioning
properly. One of these factors is a source of energy, which is gasoline
in most cars. Another factor is the engine. In the engine, the stored
chemical energy in the gasoline is converted to mechanical energy,
as a result the car moves.
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Skeletal and
Muscular
Systems
The Skeletal
System
Understanding the Human Body
2.2.1 Skeletal and Muscular Systems
Your body's mechanical parts are bones and muscles. Your body
also has a source of energy. It is food. Food provides the energy
necessary to move the mechanical parts of your body.
The Skeletal System
The skeletal system consists of bones, ligaments and cartilages.
Your body has over 200 bones, each serving many purposes, as
shown in Figure 2.1. Bones serve as a framework for your body.
Your bones work in harmony with your muscles. Bones also protect
you. Ribs and breast bones protect the heart and lungs. The skull
protects the brain.
Bone marrow is a special kind of tissue in the hollow center area of
some bones. Red blood cells are produced in marrow.
At birth, most skeletal system was composed of cartilage. Cartilage is
a connective tissue that is rigid but softer than bone. As you grew older,
ossification took place. Ossification is a process by which bone cells
and minerals replace cartilage. This process continues through
childhood and into early adulthood. However after ossification is
complete, some body parts remain as cartilage; e.g. the tip of nose
and outside of ears. Cartilage is also present as a cushion in many
joints.
The Skeletal
System and
the Health
The Skeletal System and the Health
Bones must receive sufficient amount of minerals; e.g. calcium and
phosphorous to help bone formation. They need vitamin d and some
hormones and regular exercise to help bone formation and to keep
bones strong.
Osteoporosis is a bone disease in which bone tissue becomes
brittle and porous due to deficiency of many nutrients and lack of
exercise, as a result bone fractures are likely to occur.
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Understanding the Human Body
Figure 2.1: Skeletal system
The
Muscular
System
2.2.2 The Muscular System
Body movement is controlled by a network of over 600 muscles.
These muscles make up the muscular system; see Figure 2.2. All
muscle tissue doesn’t have the same appearance. However, all
muscles have one unique characteristic, the ability to shorten, or
contract, this ability allows body movement. There are three types of
muscles in your body: skeletal, smooth and cardiac muscles:
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•
•
•
Understanding the Human Body
Skeletal muscles move the bones of the skeleton, they are
attached to bones by tough bands of tissue called tendons,
they are voluntary, and i.e. person has control over them.
Smooth muscles form the walls of many internal organs such
as the stomach, their action is involuntary, and you have no
control over them.
Cardiac muscle has character of skeletal and smooth muscles,
but it is regarded as a distinct kind of muscle. Cardiac muscle is
also involuntary muscle. It pumps blood at an average of 70
times/min., 40 million times a year for a life time.
Figure 2.2: Muscular system
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The
integumentar
y System
(Skin)
Understanding the Human Body
2.2.3 The Integumentary System (Skin)
The system that covers and protects the body is the integumentary
system, see Figure 2.3. It is composed of skin, hair follicles, nails,
glands that are outgrowths of the skin layers. The skin is the largest
organ in the body consisting of epidermis and dermis. The skin
protects by preventing harmful micro organisms from entering the
body and by regulating body temperature. Skin contains nerve
endings. Some nerve endings make you aware of changes in your
environment. Other nerve endings are sensitive to pressure, pain
and temperature.
Figure 2.3: Cross section of the layers of the skin
The Nervous
System
2.2.4 The Nervous System
It is the network of nerve cells that carries messages or impulses to
and from the brain and spinal cord to all parts of the body. The
nervous system is divided into two major parts, the central and the
peripheral nervous systems as shown in Figure 2.4.
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•
•
Sense
Organs
Understanding the Human Body
Central nervous system is composed of brain and spinal
cord. The brain is the most complex part of the central
nervous system and is protected in many ways from injury. It
has its own kind of helmet called the cranium. Brain is also
protected and nourished by three cushions called
meninges. Spaces between meninges all filled with
cerebrospinal fluid. Inner spaces of the brain are called
ventricles, it also hold fluid that protects the brain. The spinal
cord is like a thin cable that extends from the base of the
brain.
Peripheral nervous system consists of many nerves that
branch from the brain and spinal cord to the periphery of
the body. Twelve pairs of cranial nerves. Thirty -one pairs
of spinal nerves. The peripheral nervous system can be
further subdivided into two main divisions; the somatic
and autonomic nervous systems. The somatic is concerned
with a person's external environment. This system consists
of sensory and motor neurons. The autonomic involves a
person's internal environment. This part of peripheral
nervous system controls involuntary actions and regulates
heart rate and body temperature. The autonomic system is
a two-part system. One part, the sympathetic nervous
system, prepares the body for emergencies. The other part,
parasympathetic
system,
counterbalances
the
sympathetic system. This system maintains the body's
normal state and restores balance after an emergency.
Sense Organs
Your body senses play a role in everything you do. There are five
senses. You are able to experience each sense because of special
neurons that act as receptors. Receptor neurons receive information
and transmit it on sensory neurons to your spinal cord and brain. Your
brain sends back impulses on motor neurons and you respond to the
initial information. The five senses are vision, hearing, taste, smell
and touch.
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Understanding the Human Body
Figure 2.4: Nervous system
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Energy and
Transport
Systems
Understanding the Human Body
2.3 Energy and Transport Systems
The body has systems that are involved with the use of energy and
the disposal of waste products in the body cells.
• Digestive system
• Circulatory system
• Respiratory system
• Urinary system
Digestive
System
2.3.1 Digestive System
All cells need energy in order to function. Energy comes from fuel.
The fuel your body uses for energy is food. Food must be processed in
your body to provide nutrients. Digestion is the process in which
food is chemically changed to a form that can pass through cell
membrane, see Figure 2.5. When you chew solid food, teeth in your
mouth help break the food into smaller pieces. As food is chewed, it
is mixed with saliva. Saliva moistens the food and helps break down
food into simpler substances.
After food is chewed and swallowed, it moves through the esophagus
by peristalsis into the stomach. The stomach is like an elastic
pouch that acts as a temporary storage place for food. Food
remains in the stomach about four hours. The churning action of
peristalsis and the digestive juices change the food into a thick paste
called chyme. Food in this state moves into the small intestine.
Digestion is completed in the small intestine. The small intestine is a
coiled tube measuring about 7 meters (23 feet) in length.
Additional enzymes are produced in glands in the lining of small
intestine. The lining of the small intestine also contains millions of
tiny finger-like projections called villi, which increase its surface
area. Digested food is absorbed into blood vessels of the villi.
Food that is not digested pass into the large intestine (colon),
where water is absorbed. The remaining material forms a semisolid
mass called feces. The expelling of feces from the rectum is called a
bowel movement (defication). Other organs involved in digestion
and not part of the digestive tract are liver, pancreas and gall
bladder.
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Understanding the Human Body
Figure 2.5: Digestive system
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The
Digestive
System and
Health
Circulation
System
Understanding the Human Body
The Digestive System and Health
There are many common disorders that affect the digestive system.
Many are minor conditions that can be treated. Some are serious
and should be treated by a physician. Whether minor or serious, any
thing that upsets the body's ability to process food has a holistic effect.
Indigestion (dyspepsia) can be caused by gastric conditions such
as gastritis, gastric ulcer whether peptic or malignant. Hyper acidity
and duodenal ulcer are causes. Also gallbladder diseases, colonic
conditions are causes.
Appendicitis – constipation –diarrhea –hemorrhoids (piles) are
other examples and will be discussed in the lecture.
2.3.2 Circulatory System
Each body cell receives needed materials and releases waste
products. The transport of these materials to and from each body cell
is the function of the circulatory system, which is formed from the
heart, blood vessels and blood.
Blood is the fluid by which essential substances are transported to
cells throughout the body and by which waste materials are
removed from the body cells and transported to specific organs for
disposal.
The liquid part of blood is called plasma. it is about 90% water and
contains dissolved materials, including nutrients. Plasma also
contains blood cells. There are three kinds of blood cells, each with
its own unique function. These are red cells, white cells and
platelets.
The Heart
The Heart
The human heart is an incredible organ that beats between 70 and 80
times each minute, or about 100 000 times each day. The heart is a
strong muscle that lies under the sternum between lungs, as shown
in Figure 2.6. The myocardium is the muscular wall of the heart.
Within the heart are four chambers; two atria and two ventricles.
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a) Front View of Heart
Understanding the Human Body
b) Cross Section of Heart
Figure 2.6: Heart
Blood
Vessels
Blood Vessels
Blood is continually circulating in a series of closed tubes that carry
it from the heart to all body cells and back to the heart again. These
tubes are called blood vessels. There are three main types of vesselsarteries, capillaries and veins, see Figure 2.7.
Arteries carry blood from the heart to all parts of the body. Away
from the heart arteries continually subdivide into smaller arteries
called arterioles. Arterioles further subdivide to form capillaries.
Capillaries connect arterioles to small veins called venules. Blood
flowing through venules and veins is on its way back to the heart. As
blood flows through capillaries, some liquid enters into spaces
between body cells. The clear liquid is lymph. Lymph belongs to a
part of circulatory system called lymphatic system. The lymphatic
system contains lymph nodes which filter harmful organisms in the
body.
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Figure 2.7: Circulatory system
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Blood
Pressure
Understanding the Human Body
Blood pressure is the force exerted by the flowing blood against the
walls of the arteries. The pumping action of the heart creates the
force. Every time the heart beats, the pressure increases (called
systolic pressure). When the heart relaxes between beats, the
pressure decreases (called diastolic pressure). When a physician
measures your blood pressure, a measurement is taken of both the
upper and lower pressures.
A sphygmomanometer is an instrument that measures blood
pressure.
A stethoscope is an instrument that enables a physician to sound
inside a person's body.
For young adults, normal systolic blood pressure is 110-140; normal
diastolic blood pressure is 65-90.
Blood
Pressure and
Health
Respiratory
System
Blood Pressure and Health
Hypertension is the increase in blood pressure. It occurs when you
are angry or stressful or after vigorous exercise. You may have high
blood pressure without knowing it. Continued high blood pressure is
the most common disease affecting the heart and blood vessels
and can lead to serious complications. The only way to know for sure
that your blood pressure is not high is to have it measured regularly.
- Healthful behaviors for heart and blood vessels include:
• Avoid smoking.
• Reduce the amount of fat and salt in your diet.
• Practice healthful ways to deal with stress.
• Get enough exercise and rest.
2.3.3 Respiratory System
Cells to release energy from nutrients need the chemical action of
oxygen. In this process, carbon dioxide is produced as a waste
product. The respiratory system is involved in making oxygen
available to the cells and is ridding the body of carbon dioxide.
Respiration is exchange of gases between a living organism and its
environment. It takes place in two stages; external and internal, see
Figure 2.8.
- External respiration takes place as oxygen and carbon dioxide are
exchanged between blood and the air in the lungs.
- Internal respiration takes place as oxygen and carbon dioxide are
exchanged between body cells and blood circulating near them.
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Mechanics of
Breathing
Understanding the Human Body
Mechanics of Breathing
An adult inhales about 12 times each minute at rest. The process of
taking air into the lungs is called inspiration. The process of forcing air
out of the lung is called exhaling or expiration.
The
Respiratory
system and
Health
The Respiratory System and Health
Emphysema is a serious lung disease that results from the
destruction of the lung tissue. The lungs lose their elasticity and do
not function efficiently. This disease is common in people who smoke
and who regularly inhale polluted air.
Lung cancer is a leading cause of cancer death in males. The main
cause of lung cancer is cigarette smoking. Heavy smokers are 20 times
more likely to develop lung cancer than non smokers.
Figure 2.8: Respiratory system
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Urinary
System
Understanding the Human Body
2.3.4 Urinary System
This system removes wastes from the blood and helps control the
amount of fluid in the body. The organs of the urinary system are the
kidneys, ureters, bladder, and urethra, see Figure 2.9.
The kidneys lie near the lowest ribs in the back. Connected to each
kidney are an artery and vein. As blood circulates through each
kidney, the kidney acts as a filter. Waste materials that are filtered out
form urine. Urine is about 95% water in which solid wastes are
dissolved. Urine then flows into the urethras (tubes that extend from
the kidneys to the urinary bladder). The urinary bladder stores urine.
When it becomes full, nerve impulses stimulate both voluntary and
involuntary muscles to release urine from the urethra. The urethra is
a narrow tube leading from the bladder through which urine passes out
of the body.
Urinary
System and
Health
Urinary System and the Health
•
•
•
To maintain healthy kidney, it is important to have the
equivalent of at least six glasses of water in your diet daily.
Many foods you eat contain water.
Sometimes a kidney must be removed because of a disease.
In such cases, one healthy kidney can perform the task of two. If both
kidneys are removed or fail to work properly, a person may be placed
on a dialysis machine.
Dialysis
Urinalysis
Dialysis is a process in which a person's blood is filtered by a
special machine which takes the place of kidneys. The person's blood
is circulated through tubes into a filtering machine. The blood is
cleaned and then returned through a tube to the person's body. An
alternative to dialysis is a kidney transplant. It is the exchange of
unhealthy failed kidney for a healthy kidney. The healthy kidney often
comes from a blood relative of the person who receives the transplant.
This reduces the chance of rejection.
Urinalysis is the chemical examination of a person's urine. It is a
routine part of most physical examinations to detect substances that
normally are not in urine, or substances that are in larger than
normal quantities. Some people develop kidney stones. These
stones can become lodged within the kidney itself or pass into the
ureter. The danger of the stones is that they can obstruct the flow of
urine into the bladder. If the urine backs up into the kidneys it can
cause infection and destroy kidney tissue. The stones must be
removed. New advances in medicine now make it possible to
remove stones more efficiently and safely than ever before. The
lithtripter is a machine that uses a focused wave to crumble kidney
stones. No incision is needed because the shock wave passes
through body tissues without harming them. The waves hit the stones
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causing them to crumble. The pieces can be passed out of the
person's body through the urine. The use of the lithtripter is less
expensive, less painful, and requires less recovery time than
kidney stone surgery.
Figure 2.9: Urinary system
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Endocrine
and
Reproductive
Systems
Endocrine
System
Reproductive
System
Female
Reproductive
Organs
Understanding the Human Body
2.4 Endocrine System and Reproductive Systems
2.4.1 Endocrine System
Endocrine system works closely with the nervous system. It
controls functions such as growth, sexual development and the
use of food. The endocrine system consists of glands that secrete
hormones. Hormones are chemicals that act as messengers and
regulate body activities. Hormones are specific. The endocrine
glands are: pituitary, thyroid, parathyroid, adrenal medulla, thymus
pancreas testes and ovaries.
2.4.2 Reproductive System
Reproduction is the process of producing offspring. Unlike other body
systems, the reproductive system is not vital to an individual's
survival. However, this system is vital to the continuation of the
human race.
a- Female Reproductive Organs
The internal reproductive organs of the female include two ovaries,
fallopian tubes, uterus and vagina, see Figure 2.10.
Associated reproductive structures, the external parts of the female
reproductive system are known as genitalia or genitals.
The genitals include the mons veneris, labia, and clitoris. These
parts together are known as the vulva. The mammary glands of the
breasts secrete milk that can be used to nourish a baby after birth.
Milk drains through ducts to the openings in the nipples.
During puberty, the menstrual cycle begins. The menstrual cycle is a
monthly series of changes that occur in a woman's body. During
the menstrual cycle, the ovaries produce a mature egg cell, the
lining of the uterus is prepared for a fertilized egg, and the lining
breaks if an egg is not fertilized.
Female
Reproductive
Health
Female Reproductive Health
•
•
•
Women are encouraged to perform breast self examination
once a month after each menstrual period.
Any breast lump should be checked as soon as possible by
physician.
Early detection and treatment of cancer improve the chances
of cure.
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Figure 2.10: Female reproductive organs
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Male
Reproductive
System
Understanding the Human Body
b- Male Reproductive System
The main organs of the male reproductive system are the testes.
Testes are sometimes called testicles, see Figure 2.11. The other
organs of the system can be grouped as internal and external
reproductive organs.
Testes are two glands that are contained in a sac called the
scrotum. Sex hormones and reproductive cells called sperm are
produced in somniferous tubules and stored in the epididymus.
Before leaving the body, sperm move through a series of small tubes.
From the epididymus, sperm move through the vas deferens to the
prostate gland. The prostate secretes a fluid to nourish the sperm.
Behind the prostate lies the seminal vesicles; sac-like structures that
secrete fluids to help sperm motility. Sperm also receive secretions
from the Cowper's glands on either side of the urethra. From the
prostate sperm enter the ejaculatory duct (tube that leads from the
prostate to the urethra). The urethra in the male serves as a way
through the penis for both urine and sperm. However, urine and
sperm do not pass through the urethra at the same time. The urethra
extends through the penis to the outside of the body.
Circumcision is the removal of the foreskin of the penis. It is a
minor surgical procedure, done a few days after birth.
The penis is composed of three layers of spongy tissue. Many blood
vessels and nerves are supplied to this tissue. When these tissues
become filled with blood, they cause erection. Erection usually occurs
when a male is sexually stimulated. A male can have erection
without sexual stimulation. For example, awaking up in the morning
and the cause could be a full bladder or sleeping on the stomach.
Also wearing tight clothes is a cause.
Ejaculation is the release of semen from the urethra. About
teaspoon containing about 600 million sperm is released.
Male
Reproductive
Health
Male Reproductive Health
Cancer testes have increased in recent years. Early signs of this kind
of cancer may be an enlarged scrotum or a hard, painless lump in
one of the testes. A change in the testes may be found by doing a self
examination each month. Any change should be checked immediately
by a physician.
There are many other diseases that can affect the male reproductive
organs. These diseases may be transmitted through sexual contact
and are called sexually transmitted diseases (STDs).
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Figure 2.11: Male reproductive organs
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